Couplings for interconnecting fluid flow lines and holding them together under high pressures, as are used for example for supplying high pressure fluids to underground mining equipment, are known wherein a male and a female coupling member are locked together by a staple or pins. An example of such a staple-lock coupling is disclosed in Australian Patent No. 559081 (14879/83). These known staple-lock couplings are not readily able to be uncoupled in that generally separate tools have to be used to remove the staple. Furthermore, as the staple usually protrudes from the coupling, it can catch on to other pieces of equipment if the flow lines and coupling are dragged around. This can create a dangerous situation in that if sufficient force is applied to the staple it could be pulled out of the coupling causing the male and female coupling members to come apart. Should this occur while the fluid line is pressurised, a dangerous ejection of the pressurised fluid could occur, particularly if the supply side coupling member is not restrained. It is generally desirable that a coupling for use in high pressure applications and which is likely to be moved around, as in mining applications, not have any protrusions. Pin or staple-lock couplings also contain transverse holes for accommodating the pins or staple and this is undesirable because such holes provide possible entry points for water, dust etc. which may adversely affect the coupling.